Ambassador, highest rank of diplomatic representative sent by one national government to another.

At the Congress of Vienna in 1815, ambassadors were one of the four classes of diplomatic agents who were formally defined and recognized. Ambassadors were deemed to represent the person and dignity of the sovereign (or head of state) and were entitled to personal access to the sovereign to whom they were accredited. The Vienna Convention on Diplomatic Relations (1961) reduced to three the categories of diplomatic representatives, which are: (1) ambassadors and other heads of mission of equivalent rank who are accredited to the host heads of state; (2) envoys extraordinary, ministers plenipotentiary, and other representatives who are accredited to the host heads of state; and (3) chargés d’affaires, who are accredited to the foreign minister of the host country. The category of ministers-resident was omitted.

Ambassadors were originally exchanged only between the principal monarchies, with envoys or chargés d’affaires sufficing for the conduct of relations with less powerful states. Ambassadors were later also sent to republics regarded as being of equal rank. The United States appointed its first ambassadors in 1893. In 1914 there was a general exchange of ambassadors among the great powers—Austria-Hungary, France, Germany, Great Britain, Italy, Japan, Russia, and the United States—along with Spain and Turkey. Between 1919 and 1939 Belgium, China, Poland, and Portugal were raised to ambassadorial status, and since 1945, in accordance with the doctrine of the formal, legal equality of all states, most governments have sent representatives of ambassadorial rank to all countries to which they have extended diplomatic recognition.

Prior to the development of modern communications, ambassadors were frequently entrusted with extensive, even plenary, powers. They have since tended, however, to become spokesmen of their foreign offices, and rarely does an ambassador enjoy extensive discretion. An ambassador’s personality and prestige, on the other hand, may play an important part in making the views of his government understood, and his firsthand knowledge of the country to which he is accredited may enable him to influence his government’s policy decisively. See alsoextraterritoriality.